Think Froch said something about him a while back and it all escalated from there.
To be honest I think Froch is jealous of the attention Khan has received in his career. One thing I agreed with Angel Garcia was when he said Khan won a Silver medal and we turned him into a star over here. Khan had endorsements spilling out his arse before his first title win and all the TV coverage.
I'm not saying Khan hasn't paid his dues (because I think he has) but he definitely got a lot of exposure/attention too early in his career. But it's not like that's his fault but jesus who has an amateur fight broadcast on ITV the way Khan did before he turned pro.
Froch feels he had to come up the hard way to an extent and even though he's getting more coverage and exposure now, it's still not as big as a David Haye or Amir Khan.
To be honest if I was Froch I'd be pretty pissed too. A guy who I'm better than and fought better competition than, gets more exposure/praise.